(NewsNation) — President Joe Biden said making Social Security solvent is an easy fix.

“Make the very wealthy begin to pay their fair share,” he said during Thursday’s CNN debate.

Former President Donald Trump countered by saying “This man is going to single-handedly destroy Social Security,” but offered no concrete proposal, instead steering the debate back to immigration.

“Social Security … he’s destroying it because millions of people are pouring into our country and they’re putting them onto Social Security,” Trump said. “They’re putting ‘em onto Medicare and Medicaid. Putting them into hospitals. They’re taking the place of our citizens.”

Many studies have shown that illegal immigrants pay income tax and social security taxes while never receiving Social Security or Medicare benefits. A 2019 study said that, if everyone illegally in the U.S. were deported, the Social Security Trust Fund would be depleted by about $13 billion.

Biden offered details of his “fair share” plan.

“Right now, everybody making under $170,000 pays 6% of their income. Milionaires pay 1%. I have not raised the cost of Social Security for anybody under $400,000. After that I begin to make the wealthy pay their fair share by increasing (their tax rate).”

That, said Biden, will “guarantee the program for life.”

Tying Social Security to illegal immigration, Trump repeated an allegation he offered many times during the 90-minute debate:

“These millions and millions of people coming in, they’re trying to put them on Social Security. He will wipe out Social Security. He will wipe out Medicare.”

Biden countered with what he considers the most important key to saving the country’s bedrock pension and health programs.

“The biggest thing I’ll do is defeat this man because he wants to get rid of Social Security.”